Organophotoreceptor with charge transport compositions

ABSTRACT

An organophotoreceptor comprises an electrically conductive substrate and photoconductive element on the electrically conductive substrate, the photoconductive element having
         a) a charge transport composition with the formula       

     
       
         
         
             
             
         
       
         
         
           
             where Y 1  and Y 2  are, each independently, an arylamine group; 
             X 1  and X 2  are, each independently, a linking group; 
             R 1  and R 2  are, each independently, a hydrogen, an alkyl group, an alkenyl group, a heterocyclic group, an aromatic group; 
             Z is a bridging group; and 
             n is a distribution of integers between 1 and 100,000 with an average value greater than 1; and 
             (b) a charge generating compound. 
           
         
       
    
     Corresponding electrophotographic apparatuses and imaging methods are described.

FIELD OF THE INVENTION

This invention relates to organophotoreceptors suitable for use inelectrophotography and, more specifically, to organophotoreceptorshaving a charge transport composition or a polymeric charge transportmaterial comprising a polymer having repeating units comprising twohydrazone groups bonded together through a bridging group.

BACKGROUND OF THE INVENTION

In electrophotography, an organophotoreceptor in the form of a plate,disk, sheet, belt, drum or the like having an electrically insulatingphotoconductive element on an electrically conductive substrate isimaged by first uniformly electrostatically charging the surface of thephotoconductive layer, and then exposing the charged surface to apattern of light. The light exposure selectively dissipates the chargein the illuminated areas where light strikes the surface, therebyforming a pattern of charged and uncharged areas, referred to as alatent image. A liquid or dry toner is then provided in the vicinity ofthe latent image, and toner droplets or particles deposit in thevicinity of either the charged or uncharged areas to create a tonedimage on the surface of the photoconductive layer. The resulting tonedimage can be transferred to a suitable ultimate or intermediatereceiving surface, such as paper, or the photoconductive layer canoperate as an ultimate receptor for the image. The imaging process canbe repeated many times to complete a single image, for example, byoverlaying images of distinct color components or effect shadow images,such as overlaying images of distinct colors to form a full color finalimage, and/or to reproduce additional images.

Both single layer and multilayer photoconductive elements have beenused. In single layer embodiments, a charge transport composition andcharge generating material are combined with a polymeric binder and thendeposited on the electrically conductive substrate. In multilayerembodiments, the charge transport material and charge generatingmaterial are present in the element in separate layers, each of whichcan optionally be combined with a polymeric binder, deposited on theelectrically conductive substrate. Two arrangements are possible for atwo-layer photoconductive element. In one two-layer arrangement (the“dual layer” arrangement), the charge-generating layer is deposited onthe electrically conductive substrate and the charge transport layer isdeposited on top of the charge generating layer. In an alternatetwo-layer arrangement (the “inverted dual layer” arrangement), the orderof the charge transport layer and charge generating layer is reversed.

In both the single and multilayer photoconductive elements, the purposeof the charge generating material is to generate charge carriers (i.e.,holes and/or electrons) upon exposure to light. The purpose of thecharge transport material is to accept at least one type of these chargecarriers and transport them through the charge transport layer in orderto facilitate discharge of a surface charge on the photoconductiveelement. The charge transport material can be a charge transportcompound, an electron transport compound, or a combination of both. Whena charge transport compound is used, the charge transport compoundaccepts the hole carriers and transports them through the layer with thecharge transport compound. When an electron transport compound is used,the electron transport compound accepts the electron carriers andtransports them through the layer with the electron transport compound.

Organophotoreceptors may be used for both dry and liquidelectrophotography. There are many differences between dry and liquidelectrophotography. A significant difference is that a dry toner is usedin dry electrophotography, whereas a liquid toner is used in liquidelectrophotography. A potential advantage of liquid electrophotographyis that it can provide a higher resolution and thus sharper images thandry electrophotography because liquid toner particles can be generallysignificantly smaller than dry toner particles. As a result of theirsmaller size, liquid toners are able to provide images of higher opticaldensity than dry toners.

In both dry and liquid electrophotography, the charge transport materialused for the organophotoreceptor should be compatible with the polymericbinder in the photoconductive element. The selection of a suitablepolymeric binder for a particular charge transport material can placeconstraints on the formation of the photoconductive element. If thecharge transport material is not compatible with the polymeric binder,the charge transport material may phase-separate or crystallize in thepolymeric binder matrix, or may diffuse onto the surface of the layercontaining the charge transport material. If such incompatibilityoccurs, the organophotoreceptor can cease to transport charges.

Furthermore, liquid electrophotography faces an additional issue. Inparticular, the organophotoreceptor for liquid electrophotography is incontact with the liquid carrier of a liquid toner while the toner driesor pending transfer to a receiving surface. As a result, the chargetransport material in the photoconductive element may be removed byextraction by the liquid carrier. Over a long period of operation, theamount of the charge transport material removed by extraction may besignificant and, therefore, detrimental to the performance of theorganophotoreceptor.

SUMMARY OF THE INVENTION

This invention provides organophotoreceptors having good electrostaticproperties such as high V_(acc) and low V_(dis). This invention alsoprovides polymeric charge transport compositions having reducedextraction by liquid carriers and reducing the need for a polymericbinder.

In a first aspect, an organophotoreceptor comprises an electricallyconductive substrate and a photoconductive element on the electricallyconductive substrate, the photoconductive element comprising

a) a charge transport composition having the formula:

where Y₁ and Y₂ are, each independently, an arylamine group;

X₁ and X₂ are, each independently, a linking group, such as a—(CH₂)_(m)— group, where m is an integer between 1 and 30, inclusive,and one or more of the methylene groups is optionally replaced by O, S,N, C, B, Si, P, C═O, O═S═O, a heterocyclic group, an aromatic group, anNR_(a) group, a CR_(b) group, a CR_(c)R_(d) group, or a SiR_(e)R_(f)where R_(a), R_(b), R_(c), R_(d), R_(e), and R_(f) are, eachindependently, a bond, H, a hydroxyl group, a thiol group, a carboxylgroup, an amino group, an alkyl group, an alkoxy group, an alkenylgroup, a heterocyclic group, an aromatic group, or part of a ring group;

R₁ and R₂ are, each independently, a hydrogen, an alkyl group, analkenyl group, a heterocyclic group, an aromatic group;

Z is a bridging group, such as a —(CH₂)_(k)— group where k is an integerbetween 1 and 30, inclusive, and one or more of the methylene groups isoptionally replaced by O, S, N, C, B, Si, P, C═O, O═S═O, a heterocyclicgroup, an aromatic group, an NR_(g) group, a CR_(h) group, a CR_(i)R_(j)group, or a SiR_(k)R_(l) where R_(g), R_(h), R_(i), R_(j), R_(k), andR_(l) are, each independently, a bond, H, a hydroxyl group, a thiolgroup, a carboxyl group, an amino group, an alkyl group, an alkoxygroup, an alkenyl group, a heterocyclic group, an aromatic group, orpart of a ring group; and

n is a distribution of integers between 1 and 100,000 with an averagevalue of greater than one; and

(b) a charge generating compound.

The asterisks (*) indicate terminal groups on the polymer, which mayvary between different polymer units depending on the state of theparticular polymerization process at the end of the polymerization step.

The organophotoreceptor may be provided in the form of a plate, aflexible belt, a flexible disk, a sheet, a rigid drum, or a sheet arounda rigid or compliant drum. In one embodiment, the organophotoreceptorincludes: (a) a photoconductive element comprising the charge transportcomposition, the charge generating compound, a second charge transportmaterial, and a polymeric binder; and (b) the electrically conductivesubstrate.

In a second aspect, the invention features an electrophotographicimaging apparatus that includes (a) a light imaging component; and (b)the above-described organophotoreceptor oriented to receive light fromthe light imaging component. The apparatus preferably further includes atoner dispenser, such as liquid toner dispenser. The method ofelectrophotographic imaging with photoreceptors containing these novelcharge transport compounds is also described.

In a third aspect, the invention features an electrophotographic imagingprocess that includes (a) applying an electrical charge to a surface ofthe above-described organophotoreceptor; (b) imagewise exposing thesurface of the organophotoreceptor to radiation to dissipate charge inselected areas and thereby form a pattern of at least relatively chargedand uncharged areas on the surface; (c) contacting the surface with atoner, such as a liquid toner that includes a dispersion of colorantparticles in an organic liquid, to create a toned image; and (d)transferring the toned image to a substrate.

In a fourth aspect, the invention features desirable charge transportcompositions having Formula (I) above.

These photoreceptors can be used successfully with toners, such asliquid and dry toners, to produce high quality images. The high qualityof the imaging system is maintained after repeated cycling.

Other features and advantages of the invention will be apparent from thefollowing description of the preferred embodiments thereof, and from theclaims.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An organophotoreceptor as described herein has an electricallyconductive substrate and a photoconductive element comprising a chargegenerating compound and a charge transport composition or a polymericcharge transport material having repeating units comprising twohydrazone groups bonded together through a bridging group. The chargetransport composition can have desirable properties for use withinorganophotoreceptors for electrophotography. In particular, the chargetransport composition of this invention can have low solubility incarrier liquid and good compatibility with various binder materials, canbe incorporated in both the single and multilayer photoconductiveelements, and can possess excellent electrophotographic properties. Theorganophotoreceptors according to this invention generally can have ahigh photosensitivity, a low residual potential, and a high stabilitywith respect to cycle testing, crystallization, and organophotoreceptorbending and stretching. The organophotoreceptors are particularly usefulin laser printers and the like as well as photocopiers, scanners andother electronic devices based on electrophotography. The use of thesepolymeric charge transport materials is described in more detail belowin the context of laser printer use, although their application in otherdevices operating by electrophotography can be generalized from thediscussion below.

To produce high quality images, particularly after multiple cycles, itis desirable for the charge transport materials to form a homogeneoussolution with the polymeric binder and remain approximatelyhomogeneously distributed through the organophotoreceptor materialduring the cycling of the material. In addition, it is desirable toincrease the amount of charge that the charge transport material canaccept (indicated by a parameter known as the acceptance voltage or“V_(acc)”), and to reduce retention of that charge upon discharge(indicated by a parameter known as the discharge voltage or “V_(dis)”).

The charge transport materials can be classified as charge transportcompound or electron transport compound. There are many charge transportcompounds and electron transport compounds known in the art forelectrophotography. Non-limiting examples of charge transport compoundsinclude, for example, pyrazoline derivatives, fluorene derivatives,oxadiazole derivatives, stilbene derivatives, enamine derivatives,enamine stilbene derivatives, hydrazone derivatives, carbazole hydrazonederivatives, triaryl amines, polyvinyl carbazole, polyvinyl pyrene,polyacenaphthylene, or multi-hydrazone compounds comprising at least twohydrazone groups and at least two groups selected from the groupconsisting of arylamines such as (N,N-disubstituted)arylamines andheterocycles such as carbazole, julolidine, phenothiazine, phenazine,phenoxazine, phenoxathiin, thiazole, oxazole, isoxazole,dibenzo(1,4)dioxine, thianthrene, imidazole, benzothiazole,benzotriazole, benzoxazole, benzimidazole, quinoline, isoquinoline,quinoxaline, indole, indazole, pyrrole, purine, pyridine, pyridazine,pyrimidine, pyrazine, triazole, oxadiazole, tetrazole, thiadiazole,benzisoxazole, benzisothiazole, dibenzofuran, dibenzothiophene,thiophene, thianaphthene, quinazoline, or cinnoline.

Generally, an electron transport compound has an electron affinity thatis large relative to potential electron traps while yielding anappropriate electron mobility in a composite with a polymer. In someembodiments, the electron transport compound has a reduction potentialless than O₂. In general, electron transport compounds are easy toreduce and difficult to oxidize while charge transport compoundsgenerally are easy to oxidize and difficult to reduce. In someembodiments, the electron transport compounds have a room temperature,zero field electron mobility of at least about 1×10⁻¹³ cm²/Vs, infurther embodiments at least about 1×10⁻¹⁰ cm²/Vs, in additionalembodiments at least about 1×10⁻⁸ cm²/Vs, and in other embodiments atleast about 1×10⁻⁶ cm²/Vs. A person of ordinary skill in the art willrecognize that other ranges of electron mobility within the explicitranges are contemplated and are within the present disclosure.

Non-limiting examples of electron transport compounds include, forexample, bromoaniline, tetracyanoethylene, tetracyanoquinodimethane,2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone,2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone,2,6,8-trinitro-indeno4H-indeno[1,2-b]thiophene-4-one, and1,3,7-trinitrodibenzo thiophene-5,5-dioxide,(2,3-diphenyl-1-indenylidene)malononitrile, 4H-thiopyran-1,1-dioxide andits derivatives such as4-dicyanomethylene-2,6-diphenyl-4H-thiopyran-1,1-dioxide,4-dicyanomethylene-2,6-di-m-tolyl-4H-thiopyran-1,1-dioxide, andunsymmetrically substituted 2,6-diaryl-4H-thiopyran-1,1-dioxide such as4H-1,1-dioxo-2-(p-isopropylphenyl)-6-phenyl-4-(dicyanomethylidene)thiopyranand4H-1,1-dioxo-2-(p-isopropylphenyl)-6-(2-thienyl)-4-(dicyanomethylidene)thiopyran,derivatives of phospha-2,5-cyclohexadiene,alkoxycarbonyl-9-fluorenylidene)malononitrile derivatives such as(4-n-butoxycarbonyl-9-fluorenylidene)malononitrile,(4-phenethoxycarbonyl-9-fluorenylidene)malononitrile,(4-carbitoxy-9-fluorenylidene)malononitrile, anddiethyl(4-n-butoxycarbonyl-2,7-dinitro-9-fluorenylidene)malonate,anthraquinodimethane derivatives such as11,11,12,12-tetracyano-2-alkylanthraquinodimethane and11,11-dicyano-12,12-bis(ethoxycarbonyl)anthraquinodimethane, anthronederivatives such as 1-chloro-10-[bis(ethoxycarbonyl)methylene]anthrone,1,8-dichloro-10-[bis(ethoxy carbonyl)methylene]anthrone,1,8-dihydroxy-10-[bis(ethoxycarbonyl)methylene]anthrone, and1-cyano-10-[bis(ethoxycarbonyl)methylene]anthrone,7-nitro-2-aza-9-fluroenylidenemalononitrile, diphenoquinone derivatives,benzoquinone derivatives, naphtoquinone derivatives, quininederivatives, tetracyanoethylenecyanoethylene, 2,4,8-trinitrothioxantone,dinitrobenzene derivatives, dinitroanthracene derivatives,dinitroacridine derivatives, nitroanthraquinone derivatives,dinitroanthraquinone derivatives, succinic anhydride, maleic anhydride,dibromomaleic anhydride, pyrene derivatives, carbazole derivatives,hydrazone derivatives, N,N-dialkylaniline derivatives, diphenylaminederivatives, triphenylamine derivatives, triphenylmethane derivatives,tetracyanoquinodimethane, 2,4,5,7-tetranitro-9-fluorenone,2,4,7-trinitro-9-dicyanomethylenefluorenone, 2,4,5,7-tetranitroxanthonederivatives, 2,4,8-trinitrothioxanthone derivatives, 1,4,5,8-naphthalenebis-dicarboximide derivatives as described in U.S. Pat. Nos. 5,232,800,4,468,444, and 4,442,193 and phenylazoquinolide derivatives as describedin U.S. Pat. No. 6,472,514. In some embodiments of interest, theelectron transport compound comprises an(alkoxycarbonyl-9-fluorenylidene)malononitrile derivative, such as(4-n-butoxycarbonyl-9-fluorenylidene)malononitrile, and1,4,5,8-naphthalene bis-dicarboximide derivatives.

Although there are many charge transport materials available, there is aneed for other charge transport materials to meet the variousrequirements of particular electrophotography applications. Polymericcharge transport materials have the potential advantage of being lessphysically mobile within a polymer binder. In particular, if thepolymeric charge transport material is compatible with the polymerbinder, the polymers can entangle with each other such that thepolymeric charge transport material is much less susceptible toextraction by a liquid carrier associated with a liquid toner or thelike.

In electrophotography applications, a charge-generating compound withinan organophotoreceptor absorbs light to form electron-hole pairs. Theseelectrons and holes can be transported over an appropriate time frameunder a large electric field to discharge locally a surface charge thatis generating the field. The discharge of the field at a particularlocation results in a surface charge pattern that essentially matchesthe pattern drawn with the light. This charge pattern then can be usedto guide toner deposition. The polymeric charge transport materialsdescribed herein can be effective at transporting charge, holes and/orelectrons, from the electron-hole pairs formed by the charge generatingcompound. In some embodiments, a specific electron transport compound orcharge transport compound can also be used along with the polymericcharge transport material of this invention.

The layer or layers of materials containing the charge generatingcompound and the charge transport materials are within anorganophotoreceptor. To print a two dimensional image using theorganophotoreceptor, the organophotoreceptor has a two dimensionalsurface for forming at least a portion of the image. The imaging processthen continues by cycling the organophotoreceptor to complete theformation of the entire image and/or for the processing of subsequentimages.

The organophotoreceptor may be provided in the form of a plate, aflexible belt, a disk, a rigid drum, a sheet around a rigid or compliantdrum, or the like. The charge transport material can be in the samelayer as the charge generating compound and/or in a different layer fromthe charge generating compound. Additional layers can be used also, asdescribed further below.

In some embodiments, the organophotoreceptor material comprises, forexample: (a) a charge transport layer comprising the polymeric chargetransport material and a polymeric binder; (b) a charge generating layercomprising the charge generating compound and a polymeric binder; and(c) the electrically conductive substrate. The charge transport layermay be intermediate between the charge generating layer and theelectrically conductive substrate. Alternatively, the charge generatinglayer may be intermediate between the charge transport layer and theelectrically conductive substrate. In further embodiments, theorganophotoreceptor material has a single layer with both a chargetransport material and a charge generating compound within a polymericbinder.

The organophotoreceptors can be incorporated into an electrophotographicimaging apparatus, such as laser printers. In these devices, an image isformed from physical embodiments and converted to a light image that isscanned onto the organophotoreceptor to form a surface latent image. Thesurface latent image can be used to attract toner onto the surface ofthe organophotoreceptor, in which the toner image is the same or thenegative of the light image projected onto the organophotoreceptor. Thetoner can be a liquid toner or a dry toner. The toner is subsequentlytransferred, from the surface of the organophotoreceptor, to a receivingsurface, such as a sheet of paper. After the transfer of the toner, theentire surface is discharged, and the material is ready to cycle again.The imaging apparatus can further comprise, for example, a plurality ofsupport rollers for transporting a paper receiving medium and/or formovement of the photoreceptor, a light imaging component with suitableoptics to form the light image, a light source, such as a laser, a tonersource and delivery system and an appropriate control system.

An electrophotographic imaging process generally can comprise (a)applying an electrical charge to a surface of the above-describedorganophotoreceptor; (b) imagewise exposing the surface of theorganophotoreceptor to radiation to dissipate charge in selected areasand thereby form a pattern of charged and uncharged areas on thesurface; (c) exposing the surface with a toner, such as a liquid tonerthat includes a dispersion of colorant particles in an organic liquid tocreate a toner image, to attract toner to the charged or dischargedregions of the organophotoreceptor; and (d) transferring the toner imageto a substrate.

As described herein, an organophotoreceptor comprises a charge transportcomposition comprising molecules having the formula

where Y₁ and Y₂ are, each independently, an arylamine group;

X₁ and X₂ are, each independently, a linking group, such as a—(CH₂)_(m)— group, where m is an integer between 1 and 30, inclusive,and one or more of the methylene groups is optionally replaced by O, S,N, C, B, Si, P, C═O, O═S═O, a heterocyclic group, an aromatic group, anNR_(a) group, a CR_(b) group, a CR_(c)R_(d) group, or a SiR_(e)R_(f)where R_(a), R_(b), R_(c), R_(d), R_(e), and R_(f) are, eachindependently, a bond, H, a hydroxyl group, a thiol group, a carboxylgroup, an amino group, an alkyl group, an alkoxy group, an alkenylgroup, a heterocyclic group, an aromatic group, or part of a ring group;

R₁ and R₂ are, each independently, a hydrogen, an alkyl group, analkenyl group, a heterocyclic group, an aromatic group;

Z is a bridging group, such as a —(CH₂)_(k)— group where k is an integerbetween 1 and 30, inclusive, and one or more of the methylene groups isoptionally replaced by O, S, N, C, B, Si, P, C═O, O═S═O, a heterocyclicgroup, an aromatic group, an NR_(g) group, a CR_(h) group, a CR_(i)R_(j)group, or a SiR_(k)R_(l) where R_(g), R_(h), R_(i), R_(j), R_(k), andR_(l) are, each independently, a bond, H, a hydroxyl group, a thiolgroup, a carboxyl group, an amino group, an alkyl group, an alkoxygroup, an alkenyl group, a heterocyclic group, an aromatic group, orpart of a ring group; and

n is a distribution of integers between 1 and 100,000 with an averagevalue of greater than one.

The arylamine group includes, but is not limited to, an(N,N-disubstituted)arylamine group (e.g., triarylamine group,alkyldiarylamine group, and dialkylarylamine group), a julolidine group,and a carbazole group.

The heterocyclic group includes any monocyclic or polycyclic (e.g.,bicyclic, tricyclic, etc.) ring compound having at least a heteroatom(e.g., O, S, N, P, B, Si, etc.) in the ring.

An aromatic group can be any conjugated ring system containing 4n+2pi-electrons. There are many criteria available for determiningaromaticity. A widely employed criterion for the quantitative assessmentof aromaticity is the resonance energy. Specifically, an aromatic grouphas a resonance energy. In some embodiments, the resonance energy of thearomatic group is at least 10 KJ/mol. In further embodiments, theresonance energy of the aromatic group is greater than 0.1 KJ/mol.Aromatic groups may be classified as an aromatic heterocyclic groupwhich contains at least a heteroatom in the 4n+2 pi-electron ring, or asan aryl group which does not contain a heteroatom in the 4n+2pi-electron ring. The aromatic group may comprise a combination ofaromatic heterocyclic group and aryl group. Nonetheless, either thearomatic heterocyclic or the aryl group may have at least one heteroatomin a substituent attached to the 4n+2 pi-electron ring. Furthermore,either the aromatic heterocyclic or the aryl group may comprise amonocyclic or polycyclic (such as bicyclic, tricyclic, etc.) ring.

Non-limiting examples of the aromatic heterocyclic group are furanyl,thiophenyl, pyrrolyl, indolyl, carbazolyl, benzofuranyl,benzothiophenyl, dibenzofuranyl, dibenzothiophenyl, pyridinyl,pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, tetrazinyl, petazinyl,quinolinyl, isoquinolinyl, cinnolinyl, phthalazinyl, quinazolinyl,quinoxalinyl, naphthyridinyl, pteridinyl, acridinyl, phenanthridinyl,phenanthrolinyl, anthyridinyl, purinyl, pteridinyl, alloxazinyl,phenazinyl, phenothiazinyl, phenoxazinyl, phenoxathiinyl,dibenzo(1,4)dioxinyl, thianthrenyl, and a combination thereof. Thearomatic heterocyclic group may also include any combination of theabove aromatic heterocyclic groups bonded together either by a bond (asin bicarbazolyl) or by a linking group (as in 1,6di(10H-10-phenothiazinyl)hexane). The linking group may include analiphatic group, an aromatic group, a heterocyclic group, or acombination thereof. Furthermore, either an aliphatic group or anaromatic group within a linking group may comprise at least oneheteroatom such as O, S, Si, and N.

Non-limiting examples of the aryl group are phenyl, naphthyl, benzyl, ortolanyl group, sexiphenylene, phenanthrenyl, anthracenyl, coronenyl, andtolanylphenyl. The aryl group may also include any combination of theabove aryl groups bonded together either by a bond (as in biphenylgroup) or a linking group (as in stilbenyl, diphenyl sulfone, anarylamine group). The linking group may include an aliphatic group, anaromatic group, a heterocyclic group, or a combination thereof.Furthermore, either an aliphatic group or an aromatic group within alinking group may comprise at least one heteroatom such as O, S, Si, andN.

Substitution is liberally allowed on the chemical groups to affectvarious physical effects on the properties of the compounds, such asmobility, sensitivity, solubility, stability, and the like, as is knowngenerally in the art. In the description of chemical substituents, thereare certain practices common to the art that are reflected in the use oflanguage. The terms groups, central nucleus, and moiety have definedmeanings. The term group indicates that the generically recited chemicalentity (e.g., alkyl group, phenyl group, aromatic group, heterocyclicring group, epoxy group, thiiranyl group, and aziridinyl group, etc.)may have any substituent thereon which is consistent with the bondstructure of that group. For example, where the term ‘alkyl group’ isused, that term would not only include unsubstituted linear, branchedand cyclic alkyls, such as methyl, ethyl, isopropyl, tert-butyl,cyclohexyl, dodecyl and the like, but also substituents havingheteroatom, such as 3-ethoxylpropyl, 4-(N,N-diethylamino)butyl,3-hydroxypentyl, 2-thiolhexyl, 1,2,3-tribromoopropyl, and the like, andaromatic group, such as phenyl, naphthyl, carbazolyl, pyrrole, and thelike. However, as is consistent with such nomenclature, no substitutionwould be included within the term that would alter the fundamental bondstructure of the underlying group. For example, where a phenyl group isrecited, substitution such as 2- or 4-aminophenyl, 2- or4-(N,N-disubstituted)aminophenyl, 2,4-dihydroxyphenyl,2,4,6-trithiophenyl, 2,4,6-trimethoxyphenyl and the like would beacceptable within the terminology, while substitution of1,1,2,2,3,3-hexamethylphenyl would not be acceptable as thatsubstitution would require the ring bond structure of the phenyl groupto be altered to a non-aromatic form. Similarly, when referring to epoxygroup, the compound or substituent cited includes any substitution thatdoes not substantively alter the chemical nature of the epoxy ring inthe formula. When referring an (N,N-disubstituted)arylamine group, thetwo substituents attached to the nitrogen may be any group that will notsubstantively alter the chemical nature of the amine group. Where theterm moiety is used, such as alkyl moiety or phenyl moiety, thatterminology indicates that the chemical material is not substituted.Where the term alkyl moiety is used, that term represents only anunsubstituted alkyl hydrocarbon group, whether branched, straight chain,or cyclic.

Organophotoreceptors

The organophotoreceptor may be, for example, in the form of a plate, asheet, a flexible belt, a disk, a rigid drum, or a sheet around a rigidor compliant drum, with flexible belts and rigid drums generally beingused in commercial embodiments. The organophotoreceptor may comprise,for example, an electrically conductive substrate and on theelectrically conductive substrate a photoconductive element in the formof one or more layers. The photoconductive element can comprise both acharge transport material and a charge generating compound in apolymeric binder, which may or may not be in the same layer, as well asa second charge transport material such as a charge transport compoundor an electron transport compound in some embodiments. For example, thecharge transport material and the charge generating compound can be in asingle layer. In other embodiments, however, the photoconductive elementcomprises a bilayer construction featuring a charge generating layer anda separate charge transport layer. The charge generating layer may belocated intermediate between the electrically conductive substrate andthe charge transport layer. Alternatively, the photoconductive elementmay have a structure in which the charge transport layer is intermediatebetween the electrically conductive substrate and the charge generatinglayer.

The electrically conductive substrate may be flexible, for example inthe form of a flexible web or a belt, or inflexible, for example in theform of a drum. A drum can have a hollow cylindrical structure thatprovides for attachment of the drum to a drive that rotates the drumduring the imaging process. Typically, a flexible electricallyconductive substrate comprises an electrically insulating substrate anda thin layer of electrically conductive material onto which thephotoconductive material is applied.

The electrically insulating substrate may be paper or a film formingpolymer such as polyester (e.g., polyethylene terephthalate orpolyethylene naphthalate), polyimide, polysulfone, polypropylene, nylon,polyester, polycarbonate, polyvinyl resin, polyvinyl fluoride,polystyrene and the like. Specific examples of polymers for supportingsubstrates included, for example, polyethersulfone (STABAR™ S-100,available from ICI), polyvinyl fluoride (Tedlar®, available from E.I.DuPont de Nemours & Company), polybisphenol-A polycarbonate (MAKROFOL™,available from Mobay Chemical Company) and amorphous polyethyleneterephthalate (MELINAR™, available from ICI Americas, Inc.). Theelectrically conductive materials may be graphite, dispersed carbonblack, iodine, conductive polymers such as polypyrroles and Calgon®conductive polymer 261 (commercially available from Calgon Corporation,Inc., Pittsburgh, Pa.), metals such as aluminum, titanium, chromium,brass, gold, copper, palladium, nickel, or stainless steel, or metaloxide such as tin oxide or indium oxide. In embodiments of particularinterest, the electrically conductive material is aluminum. Generally,the photoconductor substrate has a thickness adequate to provide therequired mechanical stability. For example, flexible web substratesgenerally have a thickness from about 0.01 to about 1 mm, while drumsubstrates generally have a thickness from about 0.5 mm to about 2 mm.

The charge generating compound is a material that is capable ofabsorbing light to generate charge carriers, such as a dye or pigment.Non-limiting examples of suitable charge generating compounds include,for example, metal-free phthalocyanines (e.g., ELA 8034 metal-freephthalocyanine available from H.W. Sands, Inc. or Sanyo Color Works,Ltd., CGM-X01), metal phthalocyanines such as titanium phthalocyanine,copper phthalocyanine, oxytitanium phthalocyanine (also referred to astitanyl oxyphthalocyanine, and including any crystalline phase ormixtures of crystalline phases that can act as a charge generatingcompound), hydroxygallium phthalocyanine, squarylium dyes and pigments,hydroxy-substituted squarylium pigments, perylimides, polynuclearquinones available from Allied Chemical Corporation under the trade nameINDOFAST™ Double Scarlet, INDOFAST™ Violet Lake B, INDOFAST™ BrilliantScarlet and INDOFAS™ Orange, quinacridones available from DuPont underthe trade name MONASTRAL™ Red, MONASTRAL™ M Violet and MONASTRAL™ Red Y,naphthalene 1,4,5,8-tetracarboxylic acid derived pigments including theperinones, tetrabenzoporphyrins and tetranaphthaloporphyrins, indigo-and thioindigo dyes, benzothioxanthene-derivatives, perylene3,4,9,10-tetracarboxylic acid derived pigments, polyazo-pigmentsincluding bisazo-, trisazo- and tetrakisazo-pigments, polymethine dyes,dyes containing quinazoline groups, tertiary amines, amorphous selenium,selenium alloys such as selenium-tellurium, selenium-tellurium-arsenicand selenium-arsenic, cadmium sulphoselenide, cadmium selenide, cadmiumsulphide, and mixtures thereof. For some embodiments, the chargegenerating compound comprises oxytitanium phthalocyanine (e.g., anyphase thereof), hydroxygallium phthalocyanine or a combination thereof.

The photoconductive layer of this invention may optionally contain asecond charge transport material which may be a charge transportcompound, an electron transport compound, or a combination of both.Generally, any charge transport compound or electron transport compoundknown in the art can be used as the second charge transport material.

An electron transport compound and a UV light stabilizer can have asynergistic relationship for providing desired electron flow within thephotoconductor. The presence of the UV light stabilizers alters theelectron transport properties of the electron transport compounds toimprove the electron transporting properties of the composite. UV lightstabilizers can be ultraviolet light absorbers or ultraviolet lightinhibitors that trap free radicals.

UV light absorbers can absorb ultraviolet radiation and dissipate it asheat. UV light inhibitors are thought to trap free radicals generated bythe ultraviolet light and after trapping of the free radicals,subsequently to regenerate active stabilizer moieties with energydissipation. In view of the synergistic relationship of the UVstabilizers with electron transport compounds, the particular advantagesof the UV stabilizers may not be their UV stabilizing abilities,although the UV stabilizing ability may be further advantageous inreducing degradation of the organophotoreceptor over time. The improvedsynergistic performance of organophotoreceptors with layers comprisingboth an electron transport compound and a UV stabilizer are describedfurther in copending U.S. patent application Ser. No. 10/425,333 filedon Apr. 28, 2003 to Zhu, entitled “Organophotoreceptor With A LightStabilizer,” incorporated herein by reference.

Non-limiting examples of suitable light stabilizer include, for example,hindered trialkylamines such as Tinuvin 144 and Tinuvin 292 (from CibaSpecialty Chemicals, Terrytown, N.Y.), hindered alkoxydialkylamines suchas Tinuvin 123 (from Ciba Specialty Chemicals), benzotriazoles such asTinuvan 328, Tinuvin 900 and Tinuvin 928 (from Ciba SpecialtyChemicals), benzophenones such as Sanduvor 3041 (from Clariant Corp.,Charlotte, N.C.), nickel compounds such as Arbestab (from RobinsonBrothers Ltd, West Midlands, Great Britain), salicylates,cyanocinnamates, benzylidene malonates, benzoates, oxanilides such asSanduvor VSU (from Clariant Corp., Charlotte, N.C.), triazines such asCyagard UV-1164 (from Cytec Industries Inc., N.J.), polymeric stericallyhindered amines such as Luchem (from Atochem North America, Buffalo,N.Y.). In some embodiments, the light stabilizer is selected from thegroup consisting of hindered trialkylamines having the followingformula:

where R₁, R₂, R₃, R₄, R₆, R₇, R₈, R₁₀, R₁₁, R₁₂, R₁₃, R₁₄, R₁₅ are, eachindependently, hydrogen, alkyl group, or ester, or ether group; and R₅,R₉, and R₁₄ are, each independently, alkyl group; and X is a linkinggroup selected from the group consisting of —O—CO—(CH₂)_(m)—CO—O— wherem is between 2 to 20.

Optionally, the photoconductive layer may comprise a crosslinking agentlinking the charge transport compound and the binder. As is generallytrue for crosslinking agents in various contexts, the crosslinking agentcomprises a plurality of functional groups or at least one functionalgroup with the ability to exhibit multiple functionality. Specifically,a suitable crosslinking agent generally comprises at least onefunctional group that reacts with an epoxy group and at least onefunctional group that reacts with a functional group of the polymericbinder. Non-limiting examples of suitable functional groups for reactingwith the epoxy group include hydroxyl, thiol, an amino group, carboxylgroup, or a combination thereof. In some embodiments, the functionalgroup of the crosslinking agent for reacting with the polymeric binderdoes not react significantly with the epoxy group. In general, a personof ordinary skill in the art can select the appropriate functional groupof the crosslinking agent to react with the polymeric binder, orsimilarly, a person of ordinary skill in the art can select appropriatefunctional groups of the polymeric binder to react with the functionalgroup of the crosslinking agent. Suitable functional groups of thecrosslinking agent that do not react significantly with the epoxy group,at least under selected conditions, include, for example, epoxy groups,aldehydes and ketones. Suitable reactive binder functional groups forreacting with the aldehydes and ketones include, for example, amines.

In some embodiments, the crosslinking agent is a cyclic acid anhydride,which effectively is at least bifunctional. Non-limiting examples ofsuitable cyclic acid anhydrides include, for example, 1,8-naphthalenedicarboxylic acid anhydride, itaconic anhydride, glutaric anhydride andcitraconic anhydride, fumaric anhydride, phthalic anhydride, isophthalicanhydride, and terephthalic anhydride with maleic anhydride and phthalicanhydride being of particular interest.

The binder generally is capable of dispersing or dissolving the chargetransport material (in the case of the charge transport layer or asingle layer construction), the charge generating compound (in the caseof the charge generating layer or a single layer construction) and/or anelectron transport compound for appropriate embodiments. Examples ofsuitable binders for both the charge generating layer and chargetransport layer generally include, for example,polystyrene-co-butadiene, polystyrene-co-acrylonitrile, modified acrylicpolymers, polyvinyl acetate, styrene-alkyd resins, soya-alkyl resins,polyvinylchloride, polyvinylidene chloride, polyacrylonitrile,polycarbonates, polyacrylic acid, polyacrylates, polymethacrylates,styrene polymers, polyvinyl butyral, alkyd resins, polyamides,polyurethanes, polyesters, polysulfones, polyethers, polyketones,phenoxy resins, epoxy resins, silicone resins, polysiloxanes,poly(hydroxyether) resins, polyhydroxystyrene resins, novolak,poly(phenylglycidyl ether)-co-dicyclopentadiene, copolymers of monomersused in the above-mentioned polymers, and combinations thereof. Specificsuitable binders include, for example, polyvinyl butyral, polycarbonate,and polyester. Non-limiting examples of polyvinyl butyral include BX-1and BX-5 from Sekisui Chemical Co. Ltd., Japan. Non-limiting examples ofsuitable polycarbonate include polycarbonate A which is derived frombisphenol-A (e.g. Iupilon-A from Mitsubishi Engineering Plastics, orLexan 145 from General Electric); polycarbonate Z which is derived fromcyclohexylidene bisphenol (e.g. Iupilon-Z from Mitsubishi EngineeringPlastics Corp, White Plain, N.Y.); and polycarbonate C which is derivedfrom methylbisphenol A (from Mitsubishi Chemical Corporation).Non-limiting examples of suitable polyester binders includeortho-polyethylene terephthalate (e.g. OPET TR-4 from Kanebo Ltd.,Yamaguchi, Japan).

Suitable optional additives for any one or more of the layers include,for example, antioxidants, coupling agents, dispersing agents, curingagents, surfactants, and combinations thereof.

The photoconductive element overall typically has a thickness from about10 microns to about 45 microns. In the dual layer embodiments having aseparate charge generating layer and a separate charge transport layer,charge generation layer generally has a thickness form about 0.5 micronsto about 2 microns, and the charge transport layer has a thickness fromabout 5 microns to about 35 microns. In embodiments in which the chargetransport material and the charge generating compound are in the samelayer, the layer with the charge generating compound and the chargetransport composition generally has a thickness from about 7 microns toabout 30 microns. In embodiments with a distinct electron transportlayer, the electron transport layer has an average thickness from about0.5 microns to about 10 microns and in further embodiments from about 1micron to about 3 microns. In general, an electron transport overcoatlayer can increase mechanical abrasion resistance, increases resistanceto carrier liquid and atmospheric moisture, and decreases degradation ofthe photoreceptor by corona gases. A person of ordinary skill in the artwill recognize that additional ranges of thickness within the explicitranges above are contemplated and are within the present disclosure.

Generally, for the organophotoreceptors described herein, the chargegeneration compound is in an amount from about 0.5 to about 25 weightpercent, in further embodiments in an amount from about 1 to about 15weight percent, and in other embodiments in an amount from about 2 toabout 10 weight percent, based on the weight of the photoconductivelayer. The charge transport material is in an amount from about 10 toabout 80 weight percent, based on the weight of the photoconductivelayer, in further embodiments in an amount from about 35 to about 60weight percent, and in other embodiments from about 45 to about 55weight percent, based on the weight of the photoconductive layer. Theoptional second charge transport material, when present, can be in anamount of at least about 2 weight percent, in other embodiments fromabout 2.5 to about 25 weight percent, based on the weight of thephotoconductive layer, and in further embodiments in an amount fromabout 4 to about 20 weight percent, based on the weight of thephotoconductive layer. The binder is in an amount from about 15 to about80 weight percent, based on the weight of the photoconductive layer, andin further embodiments in an amount from about 20 to about 75 weightpercent, based on the weight of the photoconductive layer. A person ofordinary skill in the art will recognize that additional ranges withinthe explicit ranges of compositions are contemplated and are within thepresent disclosure.

For the dual layer embodiments with a separate charge generating layerand a charge transport layer, the charge generation layer generallycomprises a binder in an amount from about 10 to about 90 weightpercent, in further embodiments from about 15 to about 80 weight percentand in some embodiments in an amount from about 20 to about 75 weightpercent, based on the weight of the charge generation layer. Theoptional charge transport material in the charge generating layer, ifpresent, generally can be in an amount of at least about 2.5 weightpercent, in further embodiments from about 4 to about 30 weight percentand in other embodiments in an amount from about 10 to about 25 weightpercent, based on the weight of the charge generating layer. The chargetransport layer generally comprises a binder in an amount from about 20weight percent to about 70 weight percent and in further embodiments inan amount from about 30 weight percent to about 50 weight percent. Aperson of ordinary skill in the art will recognize that additionalranges of binder concentrations for the dual layer embodiments withinthe explicit ranges above are contemplated and are within the presentdisclosure.

For the embodiments with a single layer having a charge generatingcompound and a charge transport material, the photoconductive layergenerally comprises a binder, a charge transport material, and a chargegeneration compound. The charge generation compound can be in an amountfrom about 0.05 to about 25 weight percent and in further embodiment inan amount from about 2 to about 15 weight percent, based on the weightof the photoconductive layer. The charge transport material can be in anamount from about 10 to about 80 weight percent, in other embodimentsfrom about 25 to about 65 weight percent, in additional embodiments fromabout 30 to about 60 weight percent and in further embodiments in anamount from about 35 to about 55 weight percent, based on the weight ofthe photoconductive layer, with the remainder of the photoconductivelayer comprising the binder, and optional additives, such as anyconventional additives. A single layer with a charge transportcomposition and a charge generating compound generally comprises abinder in an amount from about 10 weight percent to about 75 weightpercent, in other embodiments from about 20 weight percent to about 60weight percent, and in further embodiments from about 25 weight percentto about 50 weight percent. Optionally, the layer with the chargegenerating compound and the charge transport material may comprise asecond charge transport material. The optional second charge transportmaterial, if present, generally can be in an amount of at least about2.5 weight percent, in further embodiments from about 4 to about 30weight percent and in other embodiments in an amount from about 10 toabout 25 weight percent, based on the weight of the photoconductivelayer. A person of ordinary skill in the art will recognize thatadditional composition ranges within the explicit compositions rangesfor the layers above are contemplated and are within the presentdisclosure.

In general, any layer with an electron transport compound canadvantageously further include a UV light stabilizer. In particular, theelectron transport layer generally can comprise an electron transportcompound, a binder, and an optional UV light stabilizer. An overcoatlayer comprising an electron transport compound is described further incopending U.S. patent application Ser. No. 10/396,536 to Zhu et al.entitled, “Organophotoreceptor With An Electron Transport Layer,”incorporated herein by reference. For example, an electron transportcompound as described above may be used in the release layer of thephotoconductors described herein. The electron transport compound in anelectron transport layer can be in an amount from about 10 to about 50weight percent, and in other embodiments in an amount from about 20 toabout 40 weight percent, based on the weight of the electron transportlayer. A person of ordinary skill in the art will recognize thatadditional ranges of compositions within the explicit ranges arecontemplated and are within the present disclosure.

The UV light stabilizer, if present, in any one or more appropriatelayers of the photoconductor generally is in an amount from about 0.5 toabout 25 weight percent and in some embodiments in an amount from about1 to about 10 weight percent, based on the weight of the particularlayer. A person of ordinary skill in the art will recognize thatadditional ranges of compositions within the explicit ranges arecontemplated and are within the present disclosure.

For example, the photoconductive layer may be formed by dispersing ordissolving the components, such as one or more of a charge generatingcompound, the polymeric charge transport material of this invention, asecond charge transport material such as a charge transport compound oran electron transport compound, a UV light stabilizer, and a polymericbinder in organic solvent, coating the dispersion and/or solution on therespective underlying layer and drying the coating. In particular, thecomponents can be dispersed by high shear homogenization, ball-milling,attritor milling, high energy bead (sand) milling or other sizereduction processes or mixing means known in the art for effectingparticle size reduction in forming a dispersion.

The photoreceptor may optionally have one or more additional layers aswell. An additional layer can be, for example, a sub-layer or anovercoat layer, such as a barrier layer, a release layer, a protectivelayer, or an adhesive layer. A release layer or a protective layer mayform the uppermost layer of the photoconductor element. A barrier layermay be sandwiched between the release layer and the photoconductiveelement or used to overcoat the photoconductive element. The barrierlayer provides protection from abrasion to the underlayers. An adhesivelayer locates and improves the adhesion between a photoconductiveelement, a barrier layer and a release layer, or any combinationthereof. A sub-layer is a charge blocking layer and locates between theelectrically conductive substrate and the photoconductive element. Thesub-layer may also improve the adhesion between the electricallyconductive substrate and the photoconductive element.

Suitable barrier layers include, for example, coatings such ascrosslinkable siloxanol-colloidal silica coating and hydroxylatedsilsesquioxane-colloidal silica coating, and organic binders such aspolyvinyl alcohol, methyl vinyl ether/maleic anhydride copolymer,casein, polyvinyl pyrrolidone, polyacrylic acid, gelatin, starch,polyurethanes, polyimides, polyesters, polyamides, polyvinyl acetate,polyvinyl chloride, polyvinylidene chloride, polycarbonates, polyvinylbutyral, polyvinyl acetoacetal, polyvinyl formal, polyacrylonitrile,polymethyl methacrylate, polyacrylates, polyvinyl carbazoles, copolymersof monomers used in the above-mentioned polymers, vinyl chloride/vinylacetate/vinyl alcohol terpolymers, vinyl chloride/vinyl acetate/maleicacid terpolymers, ethylene/vinyl acetate copolymers, vinylchloride/vinylidene chloride copolymers, cellulose polymers, andmixtures thereof. The above barrier layer polymers optionally maycontain small inorganic particles such as fumed silica, silica, titania,alumina, zirconia, or a combination thereof. Barrier layers aredescribed further in U.S. Pat. No. 6,001,522 to Woo et al., entitled“Barrier Layer For Photoconductor Elements Comprising An Organic PolymerAnd Silica,” incorporated herein by reference. The release layer topcoatmay comprise any release layer composition known in the art. In someembodiments, the release layer is a fluorinated polymer, siloxanepolymer, fluorosilicone polymer, silane, polyethylene, polypropylene,polyacrylate, or a combination thereof. The release layers can comprisecrosslinked polymers.

The release layer may comprise, for example, any release layercomposition known in the art. In some embodiments, the release layercomprises a fluorinated polymer, siloxane polymer, fluorosiliconepolymer, polysilane, polyethylene, polypropylene, polyacrylate,poly(methyl methacrylate-co-methacrylic acid), urethane resins,urethane-epoxy resins, acrylated-urethane resins, urethane-acrylicresins, or a combination thereof. In further embodiments, the releaselayers comprise crosslinked polymers.

The protective layer can protect the organophotoreceptor from chemicaland mechanical degradation. The protective layer may comprise anyprotective layer composition known in the art. In some embodiments, theprotective layer is a fluorinated polymer, siloxane polymer,fluorosilicone polymer, polysilane, polyethylene, polypropylene,polyacrylate, poly(methyl methacrylate-co-methacrylic acid), urethaneresins, urethane-epoxy resins, acrylated-urethane resins,urethane-acrylic resins, or a combination thereof. In some embodimentsof particular interest, the release layers are crosslinked polymers.

An overcoat layer may comprise an electron transport compound asdescribed further in copending U.S. patent application Ser. No.10/396,536, filed on Mar. 25, 2003 to Zhu et al. entitled,“Organoreceptor With An Electron Transport Layer,” incorporated hereinby reference. For example, an electron transport compound, as describedabove, may be used in the release layer of this invention. The electrontransport compound in the overcoat layer can be in an amount from about2 to about 50 weight percent, and in other embodiments in an amount fromabout 10 to about 40 weight percent, based on the weight of the releaselayer. A person of ordinary skill in the art will recognize thatadditional ranges of composition within the explicit ranges arecontemplated and are within the present disclosure.

Generally, adhesive layers comprise a film forming polymer, such aspolyester, polyvinylbutyral, polyvinylpyrrolidone, polyurethane,polymethyl methacrylate, poly(hydroxy amino ether) and the like. Barrierand adhesive layers are described further in U.S. Pat. No. 6,180,305 toAckley et al., entitled “Organic Photoreceptors for LiquidElectrophotography,” incorporated herein by reference.

Sub-layers can comprise, for example, polyvinylbutyral, organosilanes,hydrolyzable silanes, epoxy resins, polyesters, polyamides,polyurethanes, cellulosics and the like. In some embodiments, thesub-layer has a dry thickness between about 20 Angstroms and about20,000 Angstroms. Sublayers containing metal oxide conductive particlescan be between about 1 and about 25 microns thick. A person of ordinaryskill in the art will recognize that additional ranges of compositionsand thickness within the explicit ranges are contemplated and are withinthe present disclosure.

The polymeric charge transport materials as described herein, andphotoreceptors including these compounds, are suitable for use in animaging process with either dry or liquid toner development. Forexample, any dry toners and liquid toners known in the art may be usedin the process and the apparatus of this invention. Liquid tonerdevelopment can be desirable because it offers the advantages ofproviding higher resolution images and requiring lower energy for imagefixing compared to dry toners. Examples of suitable liquid toners areknown in the art. Liquid toners generally comprise toner particlesdispersed in a carrier liquid. The toner particles can comprise acolorant/pigment, a resin binder, and/or a charge director. In someembodiments of liquid toner, a resin to pigment ratio can be from 1:1 to10:1, and in other embodiments, from 4:1 to 8:1. Liquid toners aredescribed further in Published U.S. Patent Applications 2002/0128349,entitled “Liquid Inks Comprising A Stable Organosol,” and 2002/0086916,entitled “Liquid Inks Comprising Treated Colorant Particles,” and U.S.Pat. No. 6,649,316, entitled “Phase Change Developer For LiquidElectrophotography,” all three of which are incorporated herein byreference.

Charge Transport Composition

The organophotoreceptor described herein comprise a charge transportcomposition having the formula:

where Y₁ and Y₂ are, each independently, an arylamine group;

X₁ and X₂ are, each independently, a linking group, such as a—(CH₂)_(m)— group, where m is an integer between 1 and 30, inclusive,and one or more of the methylene groups is optionally replaced by O, S,N, C, B, Si, P, C═O, O═S═O, a heterocyclic group, an aromatic group, anNR_(a) group, a CR_(b) group, a CR_(c)R_(d) group, or a SiR_(e)R_(f)where R_(a), R_(b), R_(c), R_(d), R_(e), and R_(f) are, eachindependently, a bond, H, a hydroxyl group, a thiol group, a carboxylgroup, an amino group, an alkyl group, an alkoxy group, an alkenylgroup, a heterocyclic group, an aromatic group, or part of a ring group;

R₁ and R₂ are, each independently, a hydrogen, an alkyl group, analkenyl group, a heterocyclic group, an aromatic group;

Z is a bridging group, such as a —(CH₂)_(k)— group where k is an integerbetween 1 and 30, inclusive, and one or more of the methylene groups isoptionally replaced by O, S, N, C, B, Si, P, C═O, O═S═O, a heterocyclicgroup, an aromatic group, an NR_(g) group, a CR_(h) group, a CR_(i)R_(j)group, or a SiR_(k)R_(l) where R_(g), R_(h), R_(i), R_(j), R_(k), andR_(l) are, each independently, a bond, H, a hydroxyl group, a thiolgroup, a carboxyl group, an amino group, an alkyl group, an alkoxygroup, an alkenyl group, a heterocyclic group, an aromatic group, orpart of a ring group; and

n is a distribution of integers between 1 and 100,000 with an averagevalue of greater than one.

In general, the distribution of n values depends on the polymerizationconditions. The presence of the polymer of formula (1) does not precludethe presence of unreacted monomer and dimers within theorganophotoreceptor, although the concentrations of monomers and dimerswould generally be small if not extremely small or undetectable. Theextent of polymerization, as specified with n, can affect the propertiesof the resulting polymer. In some embodiments, an average value of n canbe in the hundreds or thousands, although the average value of n may beany value of 3 or greater and in some embodiments any value of 5 orgreater and in further embodiments the average value of n is 10 orgreater. A person of ordinary skill in the art will recognize thatadditional ranges of average n values are contemplated and are withinthe present disclosure.

In some embodiments, the bridging group Z may comprise an alkylenegroup, an alkenylene group, a heterocyclic group, or an aromatic group.In particular, an aromatic Z group can contribute in desirable ways tothe function of the charge transport composition. Non-limiting examplesof suitable aromatic groups include the following formulae:

where Q is a bond, O, S, O═S═O, C═O, an aryl group, an NR₃ group, or aCR₄R₅ group, where R₃, R₄, and R₅ are, each independently, H, an alkylgroup, an alkenyl group, a heterocyclic group, an aromatic group, orpart of a ring group; and

Z₁, Z₂, Z₃, and Z₄ are, each independently, a bond or a —(CH₂)_(n)—group where n is an integer between 1 and 20, inclusive, and one or moreof the methylene groups is optionally replaced by O, S, N, C, Si, B, P,C═O, O═S═O, a heterocyclic group, an aromatic group, urethane, urea, anester group, an NR₆ group, a CR₇ group, a CR₈R₉ group, or a SiR₁₀R₁₁group, where R₆, R₇, R₈, R₉, R₁₀, and R₁₁ are, each independently, abond, H, hydroxyl, thiol, carboxyl, an amino group, an alkyl group, analkoxy group, an alkenyl group, a heterocyclic group, an aromatic group,or part of a ring group.

In some embodiments, the bridging group Z has a structure according toFormula (II) above where Q is a O═S═O group and Z₁ and Z₂ are, eachindependently, a bond. In further embodiments, the charge transportcomposition has the following formula:

where n is a distribution of integers between 1 and 100,000;

Y₁ and Y₂ are, each independently, an arylamine group; and

T has one of the following formulae:

where T₁, T₂, T₃, T₄, and T₅ are, each independently, O, S, O═S═O, orC═O. Specific, non-limiting examples of suitable charge transportcomposition within the general Formula (I) of the present invention havethe following formulae:

where n is a distribution of integers between 1 and 100,000 with anaverage value of greater than one and the asterisks (*) indicateterminal groups on the polymer, which may vary between different polymerunits depending on the state of the particular polymerization process atthe end of the polymerization step.

Synthesis of Charge Transport Compositions

The synthesis of the charge transport compositions of this invention canbe prepared by the following multi-step synthetic procedure, althoughother suitable procedures can be used by a person of ordinary skill inthe art based on the disclosure herein.

The charge transport composition of this invention may be prepared bythe reaction of a multi-functional compound comprising at least 2 activehydrogens, for example, selected from the group consisting of hydroxylhydrogen, amino hydrogen, carboxyl hydrogen, and thiol hydrogen with areactive-ring compound having the following formula

where Y₁ and Y₂ are, each independently, an arylamine group;

X₃ and X₄, each independently, comprise a —(CH₂)_(p)— group, where p isan integer between 1 and 20, inclusive, and one or more of the methylenegroups is optionally replaced by O, S, N, C, B, Si, P, C═O, O═S═O, aheterocyclic group, an aromatic group, an NR_(m) group, a CR_(n) group,a CR_(o)R_(p) group, or a SiR_(q)R_(r) where R_(m), R_(n), R_(o), R_(p),R_(q), and R_(r) are, each independently, a bond, H, a hydroxyl group, athiol group, a carboxyl group, an amino group, an alkyl group, an alkoxygroup, an alkenyl group, a heterocyclic group, an aromatic group, orpart of a ring group;

R₁ and R₂ are, each independently, a hydrogen, an alkyl group, analkenyl group, a heterocyclic group, an aromatic group;

Z can comprise a —(CH₂)_(k)— group where k is an integer between 1 and30, inclusive, and one or more of the methylene groups is optionallyreplaced by O, S, N, C, B, Si, P, C═O, O═S═O, a heterocyclic group, anaromatic group, an NR_(g) group, a CR_(h) group, a CR_(i)R_(j) group, ora SiR_(k)R_(l) where R_(g), R_(h), R_(i), R_(j), R_(k), and R_(l) are,each independently, a bond, H, a hydroxyl group, a thiol group, acarboxyl group, an amino group, an alkyl group, an alkoxy group, analkenyl group, a heterocyclic group, an aromatic group, or part of aring group; and

E₁ and E₂ are, each independently, a reactive ring group, such as anepoxy ring, a thiiranyl group, an aziridinyl group, and an oxetanylgroup.

In some embodiments, the bridging group Z may comprise an alkylenegroup, an alkenylene group, a heterocyclic group, or an aromatic group.In particular, an aromatic Z group can contribute in desirable ways tothe function of the charge transport composition. Non-limiting examplesof suitable aromatic groups include the following formulae:

where Q is a bond, O, S, O═S═O, C═O, an aryl group, an NR₃ group, or aCR₄R₅ group, where R₃, R₄, and R₅ are, each independently, H, an alkylgroup, an alkenyl group, a heterocyclic group, an aromatic group, orpart of a ring group; and

Z₁, Z₂, Z₃, and Z₄, each independently, comprise a bond or a —(CH₂)_(n)—group where n is an integer between 1 and 20, inclusive, and one or moreof the methylene groups is optionally replaced by O, S, N, C, Si, B, P,C═O, O═S═O, a heterocyclic group, an aromatic group, urethane, urea, anester group, an NR₆ group, a CR₇ group, a CR₈R₉ group, or a SiR₁₀R₁₁group, where R₆, R₇, R₈, R₉, R₁₀, and R₁₁ are, each independently, abond, H, hydroxyl, thiol, carboxyl, an amino group, an alkyl group, analkoxy group, an alkenyl group, a heterocyclic group, an aromatic group,or part of a ring group.

The reactive ring groups, E₁ and E₂, are selected from the groupconsisting of heterocyclic ring groups which have a higher strain energythan its corresponding open-ring structure. The conventional definitionof strain energy is that it represents the difference in energy betweenthe actual molecule and a completely strain-free molecule of the sameconstitution. More information about the origin of strain energy can befound in the article by Wiberg et al., “A Theoretical Analysis ofHydrocarbon Properties: II Additivity of Group Properties and the Originof Strain Energy,” J. Am. Chem. Soc. 109, 985 (1987). The above articleis incorporated herein by reference. The heterocyclic ring group mayhave 3, 4, 5, 7, 8, 9, 10, 11, or 12 members, in further embodiments 3,4, 5, 7, or 8 members, in some embodiment 3, 4, or 8 members, and inadditional embodiments 3 or 4 members. Non-limiting examples of suchheterocyclic ring are cyclic ethers (e.g., epoxides and oxetane), cyclicamines (e.g., aziridine), cyclic sulfides (e.g., thiirane), cyclicamides (e.g., 2-azetidinone, 2-pyrrolidone, 2-piperidone, caprolactam,enantholactam, and capryllactam), N-carboxy-α-amino acid anhydrides,lactones, and cyclosiloxanes. The chemistry of the above heterocyclicrings is described in George Odian, “Principle of Polymerization,”second edition, Chapter 7, p. 508–552 (1981), incorporated herein byreference.

In some embodiments of interest, the reactive ring group is an epoxygroup. Some epoxy groups may have the following formula:

where R₂₁, R₂₂, and R₂₃ are, each independently, hydrogen, an alkylgroup, an alkenyl group, or an aromatic group (e.g. phenyl, naphthyl,carbazolyl, stilbenyl), or, when fused together, the atoms necessary toform a 5- or 6-member cycloaliphatic ring.

The di-epoxy-ring compound may be prepared by the following multi-stepsynthetic procedure, although other suitable procedures can be used by aperson of ordinary skill in the art based on the disclosure herein.

The first step is a nucleophilic substitution reaction between a linkingorganic compound having two halogen groups (i.e. dibromoalkanes or4,4′-dichlorodiphenyl sulfone) and hydrazine hydrate. The linkingorganic compound may or may not be symmetric with respect to the twohalogen groups. The reaction mixture may be refluxed for 24 hours. Theproduct of the nucleophilic substitution is the corresponding aromaticcompound having two hydrazine groups, such as 4,4′-dihydrazinodiphenylsulfone.

In the second step, the aromatic compound having two hydrazine groupsmay react with an arylamine having an aldehyde or a keto group to formthe corresponding aromatic compound having two hydrazone groups. Ifdesired, two different arylamine compounds can be reacted with thedi-hydrazine compound. The use of one or two arylamine reactants withketo groups result in a charge transport material with R₁ and/or R₂groups that differ from H. While the use of two different arylaminecompounds may result in a mixture of products, a person of ordinaryskill in the art can reduce the synthesis of undesired forms of productthrough either sequential or simultaneous reactions, and the differentproduct compounds can be separated from each other through appropriatepurification approaches.

In the third step, the two NH groups of the aromatic compound having twohydrazone groups may react with an organic halide comprising an epoxygroup in the presence of an alkaline to form a charge transport materialhaving two epoxidated-hydrazone groups bonded together through a linkinggroup. Non-limiting examples of suitable organic halide comprising anepoxy group for this invention are epihalohydrins, such asepichlorohydrin. The organic halide comprising an epoxy group may alsobe prepared by the epoxidation reaction of the corresponding organichalide having an olefin group. The epoxidation reaction is described inCarey et al., “Advanced Organic Chemistry, Part B: Reactions andSynthesis,” New York, 1983, pp. 494–498, incorporated herein byreference. The organic halide having an olefin group may be prepared bythe Wittig reaction between a suitable organic halide having an aldehydeor keto group and a suitable Wittig reagent. The Wittig and relatedreactions are described in Carey et al., “Advanced Organic Chemistry,Part B: Reactions and Synthesis,” New York, 1983, pp. 69–77,incorporated herein by reference. Depending on the particularreactivities of the groups, the order of some of the reactions may bechanged.

In some embodiments of interest, the E group is a thiiranyl group. Anepoxy compound, such as those described above, can be converted into thecorresponding thiiranyl compound by refluxing the epoxy compound andammonium thiocyanate in tetrahydrofuran. Alternatively, thecorresponding thiiranyl compound may be obtained by passing a solutionof the above-described epoxy compound through3-(thiocyano)propyl-functionalized silica gel (commercially availableform Aldrich, Milwaukee, Wis.). Alternatively, a thiiranyl compound maybe obtained by the thia-Payne rearrangement of a corresponding epoxycompound. The thia-Payne rearrangement is described in Rayner, C. M.Synlett 1997, 11; Liu, Q. Y.; Marchington, A. P.; Rayner, C. M.Tetrahedron 1997, 53, 15729; Ibuka, T. Chem. Soc. Rev. 1998, 27, 145;and Rayner, C. M. Contemporary Organic Synthesis 1996, 3, 499. All theabove four articles are incorporated herein by reference. For theseembodiments, X′ groups can be formed, for example, using a bifunctionalgroup with a halogen and with a thiiranyl group. The halide group can bereplaced by a bond to the secondary amine group of the hydrazone by anucleophilic substitution.

In some embodiments of interest, the E group is an aziridinyl group. Anaziridine compound may be obtained by the aza-Payne rearrangement of acorresponding epoxy compound, such as one of those epoxy compoundsdescribed above. The thia-Payne rearrangement is described in Rayner, C.M. Synlett 1997, 11; Liu, Q. Y.; Marchington, A. P.; Rayner, C. M.Tetrahedron 1997, 53, 15729; and Ibuka, T. Chem. Soc. Rev. 1998, 27,145. All the above three articles are incorporated herein by reference.Alternatively, an aziridine compound may be prepared by the additionreaction between a suitable nitrene compound and a suitable alkene. Suchaddition reaction is described in Carey et al., “Advanced OrganicChemistry, Part B: Reactions and Synthesis,” New York, 1983, pp.446–448, incorporated herein by reference. For these embodiments, X′groups can be formed, for example, using a bifunctional group with ahalogen and with an aziridinyl group. The halide group can be replacedby a bond to the secondary amine group of the hydrazone by anucleophilic substitution.

In some embodiments of interest, the E group is an oxetanyl group. Anoxetane compound may be prepared by the Paterno-Buchi reaction between asuitable carbonyl compound and a suitable alkene. The Paterno-Buchireaction is described in Carey et al., “Advanced Organic Chemistry, PartB: Reactions and Synthesis,” New York, 1983, pp. 335–336, incorporatedherein by reference. For these embodiment, X′ groups can be formed, forexample, using a bifunctional group with a halogen and with an oxetanylgroup. The halide group can be replaced by a bond to the secondary aminegroup of the hydrazone by a nucleophilic substitution.

For reaction with the reactive ring groups, the multi-functionalcompounds, such as di-functional compounds, tri-functional compounds,and tetra-functional compounds, may have two or more active hydrogenatoms, such as hydroxyl hydrogen, thiol hydrogen, amino hydrogen, andcarboxyl hydrogen. The active hydrogen atoms in any of themulti-functional compounds may be the same or different. Non-limitingexamples of tetra-functional compounds include tetra-hydroxyl compounds,tetra-thiol compounds, tetra-amino compounds, and tetra-carboxylicacids. Non-limiting examples of tri-functional compounds includetri-hydroxyl compounds, tri-thiol compounds, tri-amino compounds, andtri-carboxylic acids. The di-functional compound may be ammonia, aprimary amine, a diol, a dithiol, a diamine, a dicarboxlyic acid, ahydroxylamine, an amino acid, a hydroxyl acid, a thiol acid, ahydroxythiol, or a thioamine. Non-limiting examples of suitable dithiolare 4,4′-thiobisbenzenethiol, 1,4-benzenedithiol, 1,3-benzenedithiol,sulfonyl-bis(benzenethiol), 2,5-dimecapto-1,3,4-thiadiazole,1,2-ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol,1,5-pentanedithiol, and 1,6-hexanedithiol. Non-limiting examples ofsuitable diols are 2,2′-bi-7-naphtol, 1,4-dihydroxybenzene,1,3-dihydroxybenzene, 10,10-bis(4-hydroxyphenyl)anthrone, 4,4′-sulfonyldiphenol, bisphenol, 4,4′-(9-fluorenylidene)diphenol,1,10-decanediol, 1,5-pentanediol, diethylene glycol,4,4′-(9-fluorenylidene)-bis(2-phenoxyethanol),bis(2-hydroxyethyl)terephthalate, bis[4-(2-hydroxyethoxy)phenyl]sulfone,hydroquinone-bis(2-hydroxyethyl)ether, andbis(2-hydroxyethyl)piperazine. Non-limiting examples of suitable diamineare diaminoarenes, and diaminoalkanes. Non-limiting examples of suitabledicarboxylic acid are phthalic acid, terephthalic acid, adipic acid, and4,4′-biphenyldicarboxylic acid. Non-limiting examples of suitablehydroxylamine are p-aminophenol and fluoresceinamine. Non-limitingexamples of suitable amino acid are 4-aminobutyric acid, phenylalanine,and 4-aminobenzoic acid. Non-limiting examples of suitable hydroxyl acidare salicylic acid, 4-hydroxybutyric acid, and 4-hydroxybenzoic acid.Non-limiting examples of suitable hydroxythiol are monothiohydroquinoneand 4-mercapto-1-butanol. Non-limiting example of suitable thioamine isp-aminobenzenethiol. Non-limiting example of suitable thiol acid are4-mercaptobenzoic acid and 4-mercaptobutyric acid. Almost all of theabove di-functional compounds are available commercially from AldrichChemical Co. and other chemical suppliers.

In some embodiments, the di-functional compound may comprise twofunctional groups attached to an alkylene group, an alkenylene group, aheterocyclic group, or an aromatic group. Non-limiting examples ofsuitable aromatic group include the groups having the followingformulae:

where Q′ is a bond, O, S, O═S═O, an NR₁₂ group, or a CR₁₃R₁₄ group,where R₁₂, R₁₃, and R₁₄ are, each independently, H, an alkyl group, analkenyl group, a heterocyclic group, an aromatic group, or part of aring group; and

Z₅, Z₆, Z₇, and Z₈ are, each independently, a bond or a —(CH₂)_(q)—group where q is an integer between 1 and 20, inclusive, and one or moreof the methylene groups is optionally replaced by O, S, N, C, Si, B, P,C═O, O═S═O, a heterocyclic group, an aromatic group, urethane, urea, anester group, an NR₁₅ group, a CR₁₆ group, a CR₁₇R₁₈ group, or a SiR₁₉R₂₀group, where R₁₅, R₁₆, R₁₇, R₁₈, R₁₉, and R₂₀ are, each independently, abond, H, hydroxyl, thiol, carboxyl, an amino group, an alkyl group, analkoxy group, an alkenyl group, a heterocyclic group, an aromatic group,or part of a ring group.

Chemical bonding between the reactive-ring compound and thedi-functional compound may be promoted by using a crossing linking agentor an elevated reaction temperature. The reaction temperature may befrom 20° C. to 200° C. Preferably, the reaction temperature is between30° C. to 100° C.

Any conventional crosslinking agent for the reaction between a reactivering groups, such as epoxy group, and a functional group, such ashydroxyl, thiol, carboxyl, and an amino group, known in the art may beused for this invention. Non-limiting examples of suitable crosslinkingagent include acid anhydrides and primary or secondary amines.Non-limiting examples of suitable acid anhydride include 1,8-naphthalenedicarboxylic acid anhydride, itaconic anhydride, glutaric anhydride andcitraconic anhydride, fumaric anhydride, phthalic anhydride, isophthalicanhydride, and terephthalic anhydride with maleic anhydride and phthalicanhydride being most preferred. Non-limiting examples of suitableprimary or secondary amines include diethylene triamine, triethylenetetramine, m-phenylenediamine.

To synthesize the charge transport compositions, the degree ofpolymerization, i.e., the average value and/or distribution of n, isdetermined by the concentrations of the reactants, the reactionconditions and the reaction time. These reaction parameters can beadjusted by a person of ordinary skill in the art, based on the presentdisclosure, to obtain desired values of the extent of reaction. Ingeneral, if a one-to-one ratio is used of the reactive-ring compound andthe di-functional compound, the charge transport compositions tends tocomprise molecules with both a reactive-ring end group and a functionalgroup. A slight excess of reactive-ring compound tends to result in agreater percentage of the reactive-ring end group. Similarly, a slightexcess of the di-functional compound tends to result in a greaterpercentage of the functional end group.

More specifically, the reactive-ring compound and the di-functionalcompound react to form small molecules with more than one repeating unitas shown in Formula (I). Under sufficiently dilute reaction conditionsand a sufficiently short reaction time, the monomer compositioneffectively can be formed. To the extent that the reaction proceedsfurther, small molecules can further react with other monomer units, thereactive-ring compound and/or di-functional compound to form largermolecules that can further react. This reaction process continues untilthe reaction is stopped. The resulting product generally can becharacterized by an average molecular weight and a distribution ofmolecular weights as well as the amount of each end group. Varioustechniques used for characterizing polymers generally can be used tocharacterize correspondingly the polymers described herein.

In general, if a crosslinking agent is used, it may be desirable toreact the crosslinking agent first with either the charge transportcompound or with the polymer binder before combining the otheringredients. A person of ordinary skill in the art can evaluate theappropriate reaction order, such as combining all of the components atone time or sequentially, for forming the layer with desired properties.

While reactive ring groups provide a versatile synthesis approach forthe formation of the polymers described herein, other linking groups Yof Formula (I) above can be formed using other additive reactions thatdo not involve reactive ring groups. For example, various nucleophilicsubstitutions can be used. Some non-limiting examples of appropriatereactions include esterification reactions and amidization reactions. Aperson of ordinary skill in the art will recognize suitable reactivefunctional groups for polymerization.

The invention will now be described further by way of the followingexamples.

EXAMPLES Example 1 Synthesis and Characterization Charge TransportCompositions

This example described the synthesis and characterization ofCompositions 1–4 in which the numbers refer to formula numbers above.The characterization involves both chemical characterization and theelectronic characterization of materials formed with the compound.

Composition (1)

A suspension of 4,4′-dichlorodiphenyl sulfone (20 g, 0.069 mol, obtainedfrom Aldrich) in hydrazine hydrate (158 ml, from Aldrich) was refluxedfor 24 hours. The mixture was cooled to room temperature and crystalsprecipitated out. The crystals were filtered off and washed 3 times withwater and one time with isopropanol. The yield of the product,4,4′-dihydrazinodiphenyl sulfone, was 15.75 g (81.8%). The product had amelting point of 193–194° C. The literature procedure for thepreparation of 4,4′-dihydrazinodiphenyl sulfone was published in KhimiyaGeterotsiklicheskikh Soedinenii, 11, p. 1508–1510, 1980 (issued in theRepublic of Latvia). The article is incorporated herein by reference.

A mixture of 4-(diphenylamino)benzaldehyde (25 g, 0.09 mol, fromAldrich), 4,4′-dihydrazinodiphenyl sulfone (11.37 g, 0.041 mol) and 80ml of dioxane was added to a 250 ml round bottom flask equipped with areflux condenser and a magnetic stirrer. The reaction mixture was heatedat 50° C. for 2 hours with stirring. The solvent was removed byevaporation to form 4,4′-dihydrazondiphenyl sulfonetriphenylaminohydrazone. The yield was 30.1 g (93.4%).

A mixture of 4,4′-dihydrazondiphenyl sulfone triphenylaminohydrazone(30.1 g, 0.038 mol) and epichlorohydrin (68 ml, 0.855 mol, obtained fromAldrich) was added to a 250 ml 3-neck round bottom flask equipped with areflux condenser, a thermometer and a magnetic stirrer. The reactionmixture was stirred vigorously at 35–40° C. for 7 hours. During thistime, powdered 85% potassium hydroxide (KOH, 11.3 g, 0.171 mol) andanhydrous sodium sulfate (Na₂SO₄, 9 g, 0.0228 mol) were added in threeportions with prior cooling of the reaction mixture to 20–25° C. Afterthe termination of the reaction, the mixture was cooled to roomtemperature and filtered. The organic part was treated with ethylacetate and washed with distilled water until the pH of the water becameneutral. The organic layer was dried over anhydrous magnesium sulfate,treated with activated charcoal, and filtered. The solvents wereevaporated to form a di-epoxide. The di-epoxide was purified by columnchromatography (silica gel, grade 62, 60–200 mesh, 150 Å, Aldrich) usinga mixture of acetone and hexane in a ratio of 1:4 by volume as theeluant. The fractions containing the di-epoxide (the Composition (1)monomer precursor) were collected, and the solvents were evaporated. Thedi-epoxide was recrystallized from a mixture of acetone and hexane in aratio of 1:4 by volume and dried at 50° C. in a vacuum oven for 6 hours.The yield of the di-epoxide of 4,4′-dihydrazondiphenyl sulfonetriphenylaminohydrazone was 19.3 g (56%). The product had a meltingpoint of 223–225° C. The ¹H-NMR spectrum (100 MHz) of di-epoxide of4,4′-dihydrazondiphenyl sulfone triphenylaminohydrazone in CDCl₃ wascharacterized by the following chemical shifts (δ, ppm): 8.0–6.8 (m,38H, CH═N, Ar); 4.5–4.3 (dd, 2H, one proton of NCH₂); 4.1–3.8 (dd, 2H,another proton of NCH₂); 3.2 (m, 2H, CH); 2.9–2.8 (dd, 2H, one proton ofOCH₂); 2.7–2.5 (dd, another proton of OCH₂). An elemental analysisyielded the following results in weight percent: C 74.71; H 5.33; N9.45, which compared with calculated values for C₃₈H₃₅N₅O₂, in weightpercent of: C 74.64; H 5.37; N 9.33.

A mixture of di-epoxide of 4,4′-dihydrazondiphenyl sulfonetriphenylaminohydrazone (1 g, 1.1 mmol, prepared in the previous step),4,4′-thiobisbenzenethiol (0.275 g, 1.1 mmol, obtained from Aldrich) and15 ml of tetrahydrofuran (THF) was added to a 50 ml 3-neck round bottomflask equipped with a reflux condenser and a mechanical stirrer. Then,triethylamine (0.14 ml, 1.1 mmol, from Aldrich, Milwaukee, Wis.) wasadded to the mixture. The mixture was refluxed under argon for 60 hours.The reaction mixture was cooled to room temperature and filtered througha 3–4 cm layer of silica gel (grade 62, 60–200 mesh, 150 Å). The silicagel was washed with THF. The solution was concentrated to 15–20 ml byevaporation and then poured into a 20-fold excess of methanol withintensive stirring. The resulted precipitate was filtered off and washedrepeatedly with methanol and dried under a vacuum at 50° C. The yield ofComposition (1) was 1.08 g (84.7%).

Composition (2)

Composition (2) may be prepared according to the procedure forComposition (1) except that 9-ethyl-3-carbazolecarboxaldehyde (0.09 mol)replaces 4-(diphenylamino)benzaldehyde (0.09 mol).

Composition (3)

Composition (3) was prepared according to the procedure for Composition(1) except that 2,5-dimercapto-1,3,4-thiadiazole (0.165 g, 1.1 mmol)replaced thiobisbenzenethiol (0.275 g, 1.1 mmol). The yield ofComposition (3) was 1.01 g (86.6%).

Composition (4)

Composition (4) may be prepared according to the procedure forComposition (2) except that 2,5-dimercapto-1,3,4-thiadiazole (0.165 g,1.1 mmol) replaces thiobisbenzenethiol (0.275 g, 1.1 mmol).

Example 2 Charge Mobility Measurements

This example describes the measurement of charge mobility for samplesformed with Compositions (1) and (3) described in Example 1.

Sample 1

A mixture of 0.1 g of the Composition (1) was dissolved in 2 ml of THF.The solution was coated on the methyl cellulose coated polyester filmwith conductive Al layer by the dip roller method. After drying for 1 hat 80° C., a clear 7 μm thick layer was formed. The hole mobility of thesample was measured and the results are presented in Table 1.

Sample 2

Sample 2 was prepared and tested similarly as Sample 1, exceptComposition (1) was replaced with Composition (3) and the thickness ofthe coating was 4 μm.

Mobility Measurements

Each sample was corona charged positively up to a surface potential Uand illuminated with 2 ns long nitrogen laser light pulse. The holemobility μ was determined as described in Kalade et al., “Investigationof charge carrier transfer in electrophotographic layers of chalkogenideglasses,” Proceeding IPCS 1994: The Physics and Chemistry of ImagingSystems, Rochester, N.Y., pp. 747–752, incorporated herein by reference.The hole mobility measurement was repeated with changes to the chargingregime to charge the sample to different U values, which corresponded todifferent electric field strength inside the layer E. This dependence onelectric field strength was approximated by the formulaμ=μ₀ e ^(α√{square root over (E)}).Here E is electric field strength, μ₀ is the zero field mobility and αis Pool-Frenkel parameter. The mobility characterizing parameters μ₀ andα values as well as the mobility value at the 6.4×10⁵ V/cm fieldstrength as determined from these measurements are given in Table 1.

TABLE 1 Ionization μ₀ μ (cm²/V · s) Potential Example (cm²/V · s) at 6.4· 10⁵ V/cm α (cm/V)^(0.5) (eV) Sample 1/   8 · 10⁻⁹   2 · 10⁻⁵ 0.00985.49 Composition (1) Sample 2/ ~1 · 10⁻⁸ ~6 · 10⁻⁵ ~0.011 5.49Composition (3)

Example 3 Ionization Potential Measurements

This example describes the measurement of the ionization potential forthe 2 polymeric charge transport materials described in Example 1.

To perform the ionization potential measurements, a thin layer ofpolymeric charge transport material about 0.5 μm thickness was coatedfrom a solution of 2 mg of polymeric charge transport material in 0.2 mlof tetrahydrofuran on a 20 cm² substrate surface. The substrate waspolyester film with an aluminum layer over a methylcellulose sublayer ofabout 0.4 μm thickness.

Ionization potential was measured as described in Grigalevicius et al.,“3,6-Di(N-diphenylamino)-9-phenylcarbazole and its methyl-substitutedderivative as novel hole-transporting amorphous molecular materials,”Synthetic Metals 128 (2002), p. 127–131, incorporated herein byreference. In particular, each sample was illuminated with monochromaticlight from the quartz monochromator with a deuterium lamp source. Thepower of the incident light beam was 2–5·10⁻⁸ W. A negative voltage of−300 V was supplied to the sample substrate. A counter-electrode withthe 4.5×15 mm² slit for illumination was placed at 8 mm distance fromthe sample surface. The counter-electrode was connected to the input ofa BK2-16 type electrometer, working in the open input regime, for thephotocurrent measurement. A 10⁻¹⁵–10⁻¹² amp photocurrent was flowing inthe circuit under illumination. The photocurrent, I, was stronglydependent on the incident light photon energy hv. The I^(0.5)=f(hν)dependence was plotted. Usually, the dependence of the square root ofphotocurrent on incident light quanta energy is well described by linearrelationship near the threshold (see references “Ionization Potential ofOrganic Pigment Film by Atmospheric Photoelectron Emission Analysis,”Electrophotography, 28, Nr. 4, p. 364 (1989) by E. Miyamoto, Y.Yamaguchi, and M. Yokoyama; and “Photoemission in Solids,” Topics inApplied Physics, 26, 1–103 (1978) by M. Cordona and L. Ley, both ofwhich are incorporated herein by reference). The linear part of thisdependence was extrapolated to the hν axis, and the Ip value wasdetermined as the photon energy at the interception point. Theionization potential measurement has an error of ±0.03 eV. Theionization potential values are given in Table 1.

As understood by those skilled in the art, additional substitution,variation among substituents, and alternative methods of synthesis anduse may be practiced within the scope and intent of the presentdisclosure of the invention. The embodiments above are intended to beillustrative and not limiting. Additional embodiments are within theclaims. Although the present invention has been described with referenceto particular embodiments, workers skilled in the art will recognizethat changes may be made in form and detail without departing from thespirit and scope of the invention.

1. An organophotoreceptor comprising an electrically conductivesubstrate and a photoconductive element on the electrically conductivesubstrate, the photoconductive element comprising: (a) a chargetransport composition having the formula

where Y₁ and Y₂ are, each independently, an arylamine group; X₁ and X₂are, each independently, a linking group; R₁ and R₂ are, eachindependently, a hydrogen, an alkyl group, an alkenyl group, aheterocyclic group, an aromatic group; Z is a bridging group; and n is adistribution of integers between 1 and 100,000 with an average valuegreater than 1; and (b) a charge generating compound.
 2. Anorganophotoreceptor according to claim 1 wherein Y₁ and Y₂, eachindependently, comprise an (N,N-disubstituted)arylamine group, ajulolidine group, or a carbazole group.
 3. An organophotoreceptoraccording to claim 1 wherein X₁ and X₂ comprise, each independently, a—(CH₂)_(m)— group where m is an integer between 1 and 30, inclusive, andone or more of the methylene groups is optionally replaced by O, S, N,C, B, Si, P, C═O, O═S═O, a heterocyclic group, an aromatic group, anNR_(a) group, a CR_(b) group, a CR_(c)R_(d) group, or a SiR_(e)R_(f)where R_(a), R_(b), R_(c), R_(d), R_(e), and R_(f) are, eachindependently, a bond, H, a hydroxyl group, a thiol group, a carboxylgroup, an amino group, an alkyl group, an alkoxy group, an alkenylgroup, a heterocyclic group, an aromatic group, or part of a ring group.4. An organophotoreceptor according to claim 3 wherein at least one ofthe methylene groups is replaced by a heterocyclic group, an aromaticgroup, a CHOH group, O, or S.
 5. An organophotoreceptor according toclaim 3 wherein the charge transport composition has the followingformula:

where n is a distribution of integers between 1 and 100,000; Y₁ and Y₂are, each independently, an arylamine group; and T has one of thefollowing formulae:

where T₁, T₂, T₃, T₄, and T₅ are, each independently, O, S, O═S═O, orC═O.
 6. An organophotoreceptor according to claim 1 wherein Z comprisesa —(CH₂)_(k)— group where k is an integer between 1 and 30, inclusive,and one or more of the methylene groups is optionally replaced by O, S,N, C, B, Si, P, C═O, O═S═O, a heterocyclic group, an aromatic group, anNR_(g) group, a CR_(h) group, a CR_(i)R_(j) group, or a SiR_(k)R_(l)where R_(g), R_(h), R_(i), R_(j), R_(k), and R_(l) are, eachindependently, a bond, H, a hydroxyl group, a thiol group, a carboxylgroup, an amino group, an alkyl group, an alkoxy group, an alkenylgroup, a heterocyclic group, an aromatic group, or part of a ring group.7. An organophotoreceptor according to claim 6 wherein Z has theformulae:

where Q is a bond, O, S, O═S═O, C═O, an aryl group, an NR₃ group, or aCR₄R₅ group, where R₃, R₄, and R₅ are, each independently, H, an alkylgroup, an alkenyl group, a heterocyclic group, an aromatic group, orpart of a ring group; and Z₁, Z₂, Z₃, and Z₄ are, each independently, abond or a —(CH₂)_(n)— group where n is an integer between 1 and 20,inclusive, and one or more of the methylene groups is optionallyreplaced by O, S, N, C, Si, B, P, C═O, O═S═O, a heterocyclic group, anaromatic group, urethane, urea, an ester group, an NR₆ group, a CR₇group, a CR₈R₉ group, or a SiR₁₀OR₁₁ group, where R₆, R₇, R₈, R₉, R₁₀,and R₁₁ are, each independently, a bond, H, hydroxyl, thiol, carboxyl,an amino group, an alkyl group, an alkoxy group, an alkenyl group, aheterocyclic group, an aromatic group, or part of a ring group.
 8. Anorganophotoreceptor according to claim 7 wherein Z has the formula:

where Q is O═S═O, and Z₁ and Z₂ are, each independently, a bond.
 9. Anorganophotoreceptor according to claim 1 wherein the photoconductiveelement further comprises a second charge transport material.
 10. Anorganophotoreceptor according to claim 9 wherein the second chargetransport material comprises an electron transport compound.
 11. Anorganophotoreceptor according to claim 1 wherein the photoconductiveelement further comprises a polymer binder.
 12. An electrophotographicimaging apparatus comprising: (a) a light imaging component; and (b) anorganophotoreceptor oriented to receive light from the light imagingcomponent, the organophotoreceptor comprising an electrically conductivesubstrate and a photoconductive element on the electrically conductivesubstrate, the photoconductive element comprising: (i) a chargetransport composition having the formula

where Y₁ and Y₂ are, each independently, an arylamine group; X₁ and X₂are, each independently, a linking group; R₁ and R₂ are, eachindependently, a hydrogen, an alkyl group, an alkenyl group, aheterocyclic group, an aromatic group; Z is a bridging group; and n is adistribution of integers between 1 and 100,000 with an average ofgreater than 1; and (ii) a charge generating compound.
 13. Anelectrophotographic imaging apparatus according to claim 12 wherein Y₁and Y₂, each independently, comprise an (N,N-disubstituted)arylaminegroup, a julolidine group, or a carbazole group.
 14. Anelectrophotographic imaging apparatus according to claim 12 wherein X₁and X₂ comprise, each independently, a —(CH₂)_(m)— group where m is aninteger between 1 and 30, inclusive, and one or more of the methylenegroups is optionally replaced by O, S, N, C, B, Si, P, C═O, O═S═O, aheterocyclic group, an aromatic group, an NR_(a) group, a CR_(b) group,a CR_(c)R_(d) group, or a SiR_(e)R_(f) where R_(a), R_(b), R_(c), R_(d),R_(e), and R_(f) are, each independently, a bond, H, a hydroxyl group, athiol group, a carboxyl group, an amino group, an alkyl group, an alkoxygroup, an alkenyl group, a heterocyclic group, an aromatic group, orpart of a ring group.
 15. An electrophotographic imaging apparatusaccording to claim 14 wherein at least one of the methylene groups isreplaced by a heterocyclic group, an aromatic group, a CHOH group, O, orS.
 16. An electrophotographic imaging apparatus according to claim 12wherein Z comprises a —(CH₂)_(k)— group where k is an integer between 1and 30, inclusive, and one or more of the methylene groups is optionallyreplaced by O, S, N, C, B, Si, P, C═O, O═S═O, a heterocyclic group, anaromatic group, an NR_(g) group, a CR_(h) group, a CR_(i)R_(j) group, ora SiR_(k)R_(l) where R_(g), R_(h), R_(i), R_(j), R_(k), and R_(l) are,each independently, a bond, H, a hydroxyl group, a thiol group, acarboxyl group, an amino group, an alkyl group, an alkoxy group, analkenyl group, a heterocyclic group, an aromatic group, or part of aring group.
 17. An electrophotographic imaging apparatus according toclaim 16 wherein Z has the formulae:

where Q is a bond, O, S, O═S═O, C═O, an aryl group, an NR₃ group, or aCR₄R₅ group, where R₃, R₄, and R₅ are, each independently, H, an alkylgroup, an alkenyl group, a heterocyclic group, an aromatic group, orpart of a ring group; and Z₁, Z₂, Z₃, and Z₄ are, each independently, abond or a —(CH₂)_(n)— group where n is an integer between 1 and 20,inclusive, and one or more of the methylene groups is optionallyreplaced by O, S, N, C, Si, B, P, C═O, O═S═O, a heterocyclic group, anaromatic group, urethane, urea, an ester group, an NR₆ group, a CR₇group, a CR₈R₉ group, or a SiR₁₀R₁₁ group, where R₆, R₇, R₈, R₉, R₁₀,and R₁₁ are, each independently, a bond, H, hydroxyl, thiol, carboxyl,an amino group, an alkyl group, an alkoxy group, an alkenyl group, aheterocyclic group, an aromatic group, or part of a ring group.
 18. Anelectrophotographic imaging apparatus according to claim 17 wherein Zhas the formula:

where Q is O═S═O, and Z₁ and Z₂ are, each independently, a bond.
 19. Anelectrophotographic imaging apparatus according to claim 12 wherein thephotoconductive element further comprises an electron transportcompound.
 20. An electrophotographic imaging apparatus according toclaim 12 wherein the photoconductive element further comprises a binder.21. An electrophotographic imaging apparatus according to claim 12further comprising a toner dispenser.
 22. An electrophotographic imagingprocess comprising: (a) applying an electrical charge to a surface of anorganophotoreceptor comprising an electrically conductive substrate anda photoconductive element on the electrically conductive substrate, thephotoconductive element comprising: (i) a charge transport compositionhaving the formula

where Y₁ and Y₂ are, each independently, an arylamine group; X₁ and X₂are, each independently, a linking group; R₁ and R₂ are, eachindependently, a hydrogen, an alkyl group, an alkenyl group, aheterocyclic group, an aromatic group; Z is a bridging group; and n is adistribution of integers between 1 and 100,000 with an average greaterthan 1; and (ii) a charge generating compound; (b) imagewise exposingthe surface of the organophotoreceptor to radiation to dissipate chargein selected areas and thereby form a pattern of charged and unchargedareas on the surface; (c) contacting the surface with a toner to createa toned image; and (d) transferring the toned image to a substrate. 23.An electrophotographic imaging process according to claim 22 wherein Y₁and Y₂, each independently, comprise an (N,N-disubstituted)arylaminegroup, a julolidine group, or a carbazole group.
 24. Anelectrophotographic imaging process according to claim 22 wherein X₁ andX₂ comprise, each independently, a —(CH₂)_(m)— group where m is aninteger between 1 and 30, inclusive, and one or more of the methylenegroups is optionally replaced by O, S, N, C, B, Si, P, C═O, O═S═O, aheterocyclic group, an aromatic group, an NR_(a) group, a CR_(b) group,a CR_(c)R_(d) group, or a SiR_(e)R_(f) where R_(a), R_(b), R_(c), R_(d),R_(e), and R_(f) are, each independently, a bond, H, a hydroxyl group, athiol group, a carboxyl group, an amino group, an alkyl group, an alkoxygroup, an alkenyl group, a heterocyclic group, an aromatic group, orpart of a ring group.
 25. An electrophotographic imaging processaccording to claim 22 wherein Z comprises a —(CH₂)_(k)— group where k isan integer between 1 and 30, inclusive, and one or more of the methylenegroups is optionally replaced by O, S, N, C, B, Si, P, C═O, O═S═O, aheterocyclic group, an aromatic group, an NR_(g) group, a CR_(h) group,a CR_(i)R_(j) group, or a SiR_(k)R_(l) where R_(g), R_(h), R_(i), R_(j),R_(k), and R_(l) are, each independently, a bond, H, a hydroxyl group, athiol group, a carboxyl group, an amino group, an alkyl group, an alkoxygroup, an alkenyl group, a heterocyclic group, an aromatic group, orpart of a ring group.
 26. An electrophotographic imaging processaccording to claim 22 wherein the photoconductive element furthercomprises an electron transport compound.
 27. An electrophotographicimaging process according to claim 20 wherein the toner comprises atoner comprising colorant particles.
 28. A charge transport compositionhaving the formula:

where Y₁ and Y₂ are, each independently, an arylamine group; X₁ and X₂are, each independently, a linking group; R₁ and R₂ are, eachindependently, a hydrogen, an alkyl group, an alkenyl group, aheterocyclic group, an aromatic group; Z is a bridging group; and n is adistribution of integers between 1 and 100,000 with an average greaterthan
 1. 29. A charge transport composition according to claim 28 whereinY₁ and Y₂, each independently, comprise an (N,N-disubstituted)arylaminegroup, a julolidine group, or a carbazole group.
 30. A charge transportcomposition according to claim 28 wherein X₁ and X₂ comprise, eachindependently, a —(CH₂)_(m)— group where m is an integer between 1 and30, inclusive, and one or more of the methylene groups is optionallyreplaced by O, S, N, C, B, Si, P, C═O, O═S═O, a heterocyclic group, anaromatic group, an NR_(a) group, a CR_(b) group, a CR_(c)R_(d) group, ora SiR_(e)R_(f) where R_(a), R_(b), R_(c), R_(d), R_(e), and R_(f) are,each independently, a bond, H, a hydroxyl group, a thiol group, acarboxyl group, an amino group, an alkyl group, an alkoxy group, analkenyl group, a heterocyclic group, an aromatic group, or part of aring group.
 31. A charge transport composition according to claim 30wherein at least one of the methylene groups is replaced by aheterocyclic group, an aromatic group, a CHOH group, O, or S.
 32. Acharge transport composition according to claim 30 wherein the chargetransport composition has the following formula:

where n is a distribution of integers between 1 and 100,000 with anaverage value greater than 1; Y₁ and Y₂ are, each independently, anarylamine group; and T has one of the following formulae:

where T₁, T₂, T₃, T₄, and T₅ are, each independently, O, S, O═S═O, orC═O.
 33. A charge transport composition according to claim 28 wherein Zcomprises a —(CH₂)_(k)— group where k is an integer between 1 and 30,inclusive, and one or more of the methylene groups is optionallyreplaced by O, S, N, C, B, Si, P, C═O, O═S═O, a heterocyclic group, anaromatic group, an NR_(g) group, a CR_(h) group, a CR_(i)R_(j) group, ora SiR_(k)R_(l) where R_(g), R_(h), R_(i), R_(j), R_(k), and R_(l) are,each independently, a bond, H, a hydroxyl group, a thiol group, acarboxyl group, an amino group, an alkyl group, an alkoxy group, analkenyl group, a heterocyclic group, an aromatic group, or part of aring group.
 34. A charge transport composition according to claim 33wherein Z has the formulae:

where Q is a bond, O, S, O═S═O, C═O, an aryl group, an NR₃ group, or aCR₄R₅ group, where R₃, R₄, and R₅ are, each independently, H, an alkylgroup, an alkenyl group, a heterocyclic group, an aromatic group, orpart of a ring group; and Z₁, Z₂, Z₃, and Z₄ are, each independently, abond or a —(CH₂)_(n)— group where n is an integer between 1 and 20,inclusive, and one or more of the methylene groups is optionallyreplaced by O, S, N, C, Si, B, P, C═O, O═S═O, a heterocyclic group, anaromatic group, urethane, urea, an ester group, an NR₆ group, a CR₇group, a CR₈R₉ group, or a SiR₁₀R₁₁ group, where R₆, R₇, R₈, R₉, R₁₀,and R₁₁ are, each independently, a bond, H, hydroxyl, thiol, carboxyl,an amino group, an alkyl group, an alkoxy group, an alkenyl group, aheterocyclic group, an aromatic group, or part of a ring group.
 35. Acharge transport composition according to claim 34 wherein Z has theformulae:

where Q is O═S═O, and Z₁ and Z₂ are, each independently, a bond.
 36. Acharge transport composition prepared by co-polymerizing amulti-functional compound comprising at least 2 active hydrogensselected form the group consisting of hydroxyl hydrogen, amino hydrogen,carboxyl hydrogen, and thiol hydrogen with a reactive-ring compoundhaving the following formula

where Y₁ and Y₂ are, each independently, an arylamine group; X₃ and X₄,each independently, comprise a —(CH₂)_(p)— group, where p is an integerbetween 1 and 20, inclusive, and one or more of the methylene groups isoptionally replaced by O, S, N, C, B, Si, P, C═O, O═S═O, a heterocyclicgroup, an aromatic group, an NR_(m) group, a CR_(n) group, a CR_(o)R_(p)group, or a SiR_(q)R_(r) where R_(m), R_(n), R_(o), R_(p), R_(q), andR_(r) are, each independently, a bond, H, a hydroxyl group, a thiolgroup, a carboxyl group, an amino group, an alkyl group, an alkoxygroup, an alkenyl group, a heterocyclic group, an aromatic group, orpart of a ring group; R₁ and R₂ are, each independently, a hydrogen, analkyl group, an alkenyl group, a heterocyclic group, an aromatic group;Z comprises a —(CH₂)_(k)— group where k is an integer between 1 and 30,inclusive, and one or more of the methylene groups is optionallyreplaced by O, S, N, C, B, Si, P, C═O, O═S═O, a heterocyclic group, anaromatic group, an NR_(g) group, a CR_(h) group, a CR_(i)R_(j) group, ora SiR_(k)R_(l) where R_(g), R_(h), R_(i), R_(j), R_(k), and R_(l) are,each independently, a bond, H, a hydroxyl group, a thiol group, acarboxyl group, an amino group, an alkyl group, an alkoxy group, analkenyl group, a heterocyclic group, an aromatic group, or part of aring group; and E₁ and E₂ are, each independently, a reactive ringgroup.
 37. A charge transport composition according to claim 36 whereinE₁ and E₂, each independently, are selected from the group consisting of3-, 4-, 5-, 7-, 8-, 9-, 10-, 11-, and 12-membered heterocyclic ringgroups.
 38. A charge transport composition according to claim 36 whereinE₁ and E₂, each independently, are selected from the group consisting of3-, 4-, 5-, 7-, 8-, 9-, 10-, 11-, and 12-membered cyclic ethers, cyclicamines, cyclic sulfides, cyclic amides, N-carboxy-a-amino acidanhydrides, lactones, and cyclosiloxanes.
 39. A charge transportcomposition according to claim 36 wherein E₁ and E₂, each independently,are selected from the group consisting of epoxides, oxetanes,aziridines, thiiranes, 2-azetidinone, 2-pyrrolidone, 2-piperidone,caprolactam, enantholactam, and capryllactam.
 40. A charge transportcomposition according to claim 36 wherein the multi-functional compoundis selected from the group consisting of triols, triamines, trithiols,diols, dithiols, diamines, dicarboxlyic acids, hydroxylamines, aminoacids, hydroxyl acids, thiol acids, hydroxythiosl, and thioamines.